Population genetic theory will be developed to predict levels of variation and degrees of association for genetic markers in a variety of population structures, mating systems and mutation regimes. Particular attention will be paid to electrophoretic and restriction fragment markers, and to complete DNA sequences. Theoretical models will be accompanied by statistical methodologies for making inferences from these various kinds of data. Work will proceed in four principal directions. The first will be concerned with predicting, and estimating, sample variances for a range of statistics such as heterozygosity and gene diversity. Variation introduced by choice of population, choice of individuals, and choice of loci will be combined, and evaluated for a range of mating systems. A second aim will be to develop methodologies for the efficient estimation of a suite of one-and two-locus descent measures. The behavior of these descent measures under different mutation regimes will also be determined. The third area of investigation will cover measures of disequilibrium, with attention to the effects of drift on disequilibrium between, say, restriction sites and loci of interest. Tests for high order disequilibria will be developed, and amalgamation over many pairs of alleles and loci will be studied. Finally, the application of statistical genetics to DNA sequences will be undertaken, with an aim of incorporating within-population variation into between-population comparisons, and in determining the power of tests of sequence dissimilarity.